Patient controlled atrial shock therapy

ABSTRACT

An implanted cardiac device detects an atrial arrhythmia and provides periodically updated atrial arrhythmia status as long as the arrhythmia is ongoing. A patient may request an indication of ongoing atrial arrhythmia status from external to the patient using a patient activator. The patient activator may include a magnet for closing a reed switch in the implanted device to provide the request or may provide the request over a telemetry link to the implanted device. The implanted device may provide the requested atrial arrhythmia status and other information in the form of an audible tone produced by the implanted device or as a message telemetered from the implanted device to the patient activator. The patient activator may include a tone detector and display for providing a visual indication of the atrial arrhythmia status indication. The magnet activator may also be employed to request or withhold atrial shock therapy.

FIELD OF THE INVENTION

[0001] The present invention pertains generally to medical devices andmore particularly to implantable medical devices such as devices formonitoring activity of the heart and providing electrical shock therapythereto including automatic implantable cardioverter defibrillatordevices for treating atrial arrhythmias and external patient operabledevices for monitoring and controlling the operation of such implantablemedical devices.

BACKGROUND OF THE INVENTION

[0002] Various types of medical devices are employed to monitorelectrical or other activity of the heart and to provide therapy to theheart in response to the detection of irregular cardiac rhythms. Suchdevices may be implantable beneath the skin of a patient, i.e., in thepatient's chest. Such implantable devices include a hermetically sealedcanister containing electronic circuitry for implementing the functionsof the device, one or more electrodes implanted in one or more of thechambers of the heart, or in close proximity thereto, and leads forconnecting the electrodes to the circuitry within the device canister.The device circuitry includes circuitry for detecting electrical signalsproduced by the heart, which signals are picked up at the electrodes,along with circuitry, typically implemented in a microprocessor, foranalyzing the thus-detected cardiac signals. The device may also includecircuitry for providing therapy in the form of electric shock signalsapplied to the heart. Such signals are provided to the heart, via theleads and electrodes mounted in the heart, in response to the detectionof an irregular cardiac rhythm by the analysis circuitry based on thedetected cardiac activity signals. The implantable device may alsoinclude a transmitter/receiver, for transmitting cardiac activity andother information to an external device for, e.g., storage and/orfurther analysis, and for receiving information, such as programminginstructions, from the external device via, for example, an RF link.

[0003] An example of such an implantable cardiac device is an automaticimplantable cardioverter defibrillator (AICD) for treating atrialarrhythmias, e.g., atrial tachycardia, fibrillation, flutter, etc. (Thefunctionality of an atrial AICD may be combined with those of abradycardia pacemaker, ventricular defibrillator, etc.) Atrialarrhythmias are probably the most common cardiac arrhythmia. Althoughatrial arrhythmias are not usually life-threatening, patients withatrial arrhythmias generally experience palpitations of the heart, andmay experience dizziness or even loss of consciousness. Atrialarrhythmias, such as atrial fibrillation, also have been associated withstrokes and other conditions. Atrial arrhythmias can occur suddenly.Implantable atrial cardioverter defibrillators are programmed to detectthe onset of atrial arrhythmias and to provide an appropriate electricalshock therapy to the atria to terminate the atrial arrhythmia. Theatrial shock therapy to be provided may depend upon the type of atrialarrhythmia detected, e.g., atrial tachycardia versus atrialfibrillation. Shock therapy provided by an implantable atrialcardioverter defibrillator may include a relatively high voltage levelatrial defibrillation or cardioversion pulse, which is typicallydelivered to the atria in synchronism with a detected or pacedventricular activation, to terminate atrial fibrillation or flutter.Atrial antitachycardia pacing may be applied by the implantable deviceto terminate atrial tachycardia. Atrial antitachycardia pacing typicallyinvolves a train of pacing pulses applied to the atria at a rateslightly higher than the rate of the tachycardia.

[0004] Various systems and methods have been developed to allow patientshaving implanted atrial cardioverter defibrillators to monitor andcontrol, to at least some degree, operation of the implanted device. Forexample, U.S. Pat. No. 5,490,862 describes an implantable atrialdefibrillator which may be programmed to operate in a patient activatedmode of operation. In the patient activated mode, an atrial fibrillationintervention sequence is performed by the implanted device in responseto the receipt of a sequence command generated from external to thepatient. The sequence command may be generated, for example, by anexternal magnet applied by the patient to near the implantation site, toclose and then open a reed switch mounted in the implanted device andcoupled to the device microprocessor. The intervention sequence thusinitiated by the patient, when he believes he is experiencing an atrialarrhythmia, includes atrial fibrillation detection by the implanteddevice and, if atrial fibrillation is confirmed, the application ofcardioverting electrical energy to the atria.

[0005] U.S. Pat. No. 5,674,249 describes the use of a portablecommunication device which allows a patient to monitor and control theoperation of an implanted atrial defibrillator. The portablecommunication device, which may be dimensioned to be hand held by apatient, includes a transmitter/receiver for communicating with theimplanted device via a telemetry (e.g., RF) link. In this system, anatrial fibrillation intervention sequence may be initiated in animplanted device in response to a sequence command generated from theportable communication device. The patient may also use the portablecommunication device to program the implanted device into an automaticmode wherein the intervention sequence is initiated automatically atpredetermined times. The handheld portable communication device receivesan acknowledgment signal from the implanted device when a command signalsent from the communication device is received by the implanted device.The receipt of the acknowledgment signal by the portable handheldcommunication device is displayed to the patient on the device. Thedisplay includes a description of the task being performed by theimplanted device in response to the command signal sent by the patient.Thus, a patient is able to both monitor and control operation of animplanted cardiac device to some degree.

[0006] U.S. Pat. No. 5,999,851 describes an implantable atrialdefibrillator which includes an atrial fibrillation detection only modeof operation. In this mode, atrial fibrillation detection is initiatedin the implanted device by a command signal sent from an externalpatient operated communication device, which is in communication withthe implanted defibrillator via a telemetry (e.g., RF) link. If atrialfibrillation is detected by the implanted atrial defibrillator, anappropriate signal is communicated to the patient operated communicationdevice, and a visual and/or audible message is provided by thecommunication device to the patient to indicate whether or not atrialfibrillation is detected. In this detection only mode, a further signalmust be provided from the communication device to the implanted deviceto initiate cardioversion therapy, preferably after continued atrialfibrillation is confirmed by the implanted device.

[0007] In each of the systems described above, atrial fibrillationdetection, or atrial fibrillation detection followed by atrial shocktherapy, if required, may be initiated by a patient using an externalcommunication device. To monitor the progress of an ongoing atrialarrhythmia event in such systems, a patient must repeatedly signal theimplanted device to reinitiate atrial fibrillation detection.Furthermore, to both monitor the status of an atrial arrhythmia detectedby the implanted device and control the providing of shock therapy tothe atria by the implanted device a relatively complicated externalcommunication device employing a telemetry link is used to provide avariety of control signals from the communication device to theimplanted device.

[0008] What is desired is an atrial shock therapy system which allows apatient to monitor the status of an ongoing atrial arrhythmia eventwithout requiring repeated reinitiation by the patient of atrialarrhythmia detection. Preferably, a relatively simple and inexpensivepatient controlled activator or communication device may be employed bythe patient both to monitor atrial event status as determined by animplanted device as well as to control the providing of atrial shocktherapy by the implanted device.

SUMMARY OF THE INVENTION

[0009] The present invention provides a system and method which allows apatient with an implanted automatic implantable cardioverterdefibrillator to monitor the status of an atrial arrhythmia detected bythe implanted device and to control the providing of shock therapy tothe atria by the device. In accordance with the present invention, apatient employs an external activator communication device to request anindication of the status of an ongoing atrial arrhythmia event withoutrequiring repeated initiation of atrial event detection by the implanteddevice. The patient activator communication device may preferably beimplemented in a relatively simple and inexpensive manner and allow thepatient both to request atrial arrhythmia event status as well as tocontrol the providing of electrical shock therapy to the atria by theimplanted device to terminate an atrial arrhythmia event.

[0010] The present invention may be implemented in an implantablecardiac device, such as an automatic implantable cardioverterdefibrillator, which provides atrial arrhythmia detection and electricalshock therapy to the atria to terminate such atrial arrhythmias. (Theimplantable device may also include ventricular arrhythmia monitoringand ventricular shock therapy functionality and/or ventricular pacingfunctionality, as well as atrial pacing capability.) The implantablecardiac device includes signal detection circuitry, connected via leadsto electrodes positioned in the atria and, preferably, the ventricles ofthe heart, to detect electrical heart activity signals. An implanteddevice system processor monitors the output provided by the signaldetection circuitry to detect the occurrence of an atrial arrhythmia,e.g., atrial tachycardia, fibrillation, and/or flutter, using knownatrial arrhythmia detection algorithms. The implantable device includescardioverter/defibrillator circuitry, controlled by the deviceprocessor, for providing defibrillation shock therapy, and/orantitachycardia pacing, depending upon the type of atrial arrhythmiaidentified, to the atria via the leads and electrodes implanted in theheart. The implantable device is preferably also provided with atelemetry receiver/transmitter, coupled to the device processor, toallow the processor to transmit cardiac activity and other data to anexternal programmer device for storage and/or further analysis, and toreceive data, such as programming instructions, from the externalprogrammer device. The external programmer device is a relativelycomplicated device used by a physician to program the implanted deviceand query cardiac activity data therefrom.

[0011] In accordance with the present invention, a patient, having animplanted cardiac device in accordance with the present invention, isable to monitor an atrial arrhythmia detected by the implanted deviceand control the providing of atrial shock therapy by the implanteddevice using a patient activator communication device. The patientactivator is preferably a relatively small, handheld device, whichallows the patient to initiate a patient activation operation in theimplantable device to determine the status of an atrial arrhythmia eventdetected by the implanted device (if any) as well as, preferably, tocontrol the providing of shock therapy to the atria by the implantabledevice to terminate the atrial arrhythmia event. The patient activatorpreferably employs a relatively simple mechanism for initiating apatient activation operation. For example, the patient activator mayinclude a magnet which, when placed near the implantation site of theimplanted device, operates a reed switch in the implanted device, whichis coupled to the implanted device processor, thereby to initiate apatient activation operation.

[0012] In response to the receipt of a patient activation request, theimplanted device provides information indicating the status of anyongoing atrial arrhythmia detected thereby to the patient. For example,the implanted device may include a tone-producing circuit, for driving asmall speaker, which produces distinctive tones, audible to the patient,which indicate that the implanted device has received the patientactivation request and whether or not an atrial arrhythmia is ongoing.The implanted device continually monitors and updates the status of anongoing atrial arrhythmia event. Periodically, e.g., every ventricularcycle, the implanted device updates the tone, or other signal, producedby the implanted device, to indicate to a patient any change in thestatus of the atrial arrhythmia event, as long as the patient activationrequest is provided by the activator. Thus, information on the changingstatus of an atrial arrhythmia event is provided periodically to apatient, e.g., as long as the patient activator is positioned near theimplantation site. In accordance with the present invention, a patientis not required to reinitiate periodically atrial arrhythmia detectionby the implanted device in order to obtain current atrial arrhythmiaevent status information.

[0013] The implanted device may also provide other information to thepatient, such as the availability of the implanted device to provideatrial shock therapy, in response to the initiation of an activationrequest by the patient using the patient activator. For example,different audible tones may be produced by the implanted devicedepending on both whether or not an atrial arrhythmia event is occurringand/or whether or not atrial shock therapy is available.

[0014] The patient activator communication device may also provide avisual indication to the patient indicating the ongoing status of anatrial arrhythmia event and/or the availability of atrial shock therapy.For example, the patient activator device may include tone detectioncircuitry which detects the various tones produced by the implanteddevice in response to a patient initiated activation request. The tonedetection circuitry converts such tones into electrical signals, whichmay be analyzed by an activator processor, which, in turn, drives adisplay (e.g., an LED or lamp display) on the activator to provide aperiodically updated visual indication of atrial arrhythmia event statusand/or atrial shock therapy availability (as long as a patientactivation request is provided from the activator to the implanteddevice).

[0015] The patient activator communication device may also be employedto control the providing of atrial shock therapy by the implanteddevice. For example, a patient activation operation, as described above,may be initiated by positioning the patient activator device magnet nearthe implantable device implant site for at least a relatively shortinitial duration (e.g., one second). In response to the presence of thepatient activator device, the implantable device provides an indicationto the patient (e.g., audibly) of the status of any detected atrialarrhythmia event. If the patient activator device is removed from nearthe implantation site shortly thereafter (i.e., within less than athreshold duration, e.g., seven seconds, from initial application of theactivator to the implantation site), atrial shock therapy will bewithheld (i.e., disabled), and no atrial shock therapy will be providedeven though an atrial arrhythmia has been detected and atrial shocktherapy is otherwise available. However, if the patient activationoperation is maintained for a longer period (e.g., more than thethreshold duration), e.g., by maintaining the patient activator devicemagnet in position for more than the threshold duration, appropriateshock therapy (e.g., synchronized cardioversion and/or antitachycardiapacing, depending upon the nature of the atrial arrhythmia) will berequested and provided by the implantable device, e.g., after thepatient activator is removed from the implant site. If the patientactivation operation is maintained for an even longer period (e.g.,longer than a stop therapy threshold duration, which may be, forexample, sixty seconds), e.g., by maintaining the patient activatordevice magnet in position for longer than the stop therapy thresholdduration, any shock therapy initiated in the implantable device may bedisabled (until the patient activator is removed from position near theimplant site and then replaced in position near the implant site for atleast the initial duration to re-initiate a patient activationoperation). Thus, a patient is able to employ a relatively simple andinexpensively implemented patient activator (e.g., a magnet) to bothmonitor atrial arrhythmia event status as detected by an implanteddevice as well as to control the providing of shock therapy to the atriaby the implanted device to terminate the detected atrial arrhythmiaevent. In more general terms, in accordance with the present invention,the presence of a patient activation request may be used to request anatrial arrhythmia event status indication from an implanted device,while the duration of the same request signal is used to control theproviding of atrial shock therapy by the implanted device.

[0016] Although a relatively simple and inexpensive patient activatordevice, e.g., including a magnet, tone detector circuitry, a processor,and a status display, may be employed in accordance with the presentinvention, a more complicated patient activator may also be used. A morecomplicated patient activator communication device may include areceiver/transmitter for communicating control signals to and receivingstatus information signals from the implanted cardiac device via atelemetry (e.g., RF) link with a corresponding receiver/transmitter inthe implanted device. Such a patient activator communication device mayinclude a patient input circuit, including buttons, switches, etc., forallowing a patient to signal via the telemetry link from the activatorto the implanted device to initiate a patient activation operation.Atrial arrhythmia event status information may be communicated, inresponse to receipt of the activation request by the implanted device,from the implanted device to the activator over the telemetry link. Suchstatus information may be displayed or otherwise presented in visual oraudible form to the patient by the activator device. The patientactivator may also employ telemetry to request and receive statusinformation from the implanted device regarding the availability ofatrial shock therapy, as well as to control the providing of atrialshock therapy by the implanted device.

[0017] Further objects, features, and advantages of the invention willbe apparent from the following detailed description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In the drawings:

[0019]FIG. 1 is a schematic block diagram of an exemplary implantablecardiac device for detecting atrial arrhythmias and providing electricalshock therapy to the atria, and a patient activator communication devicefor controlling the implantable device to provide atrial arrhythmiaevent status information to the patient and to control the providing ofshock therapy to the atria by the implantable device.

[0020]FIG. 2 is a more detailed schematic block diagram of an exemplarypatient activator communication device in accordance with the presentinvention.

[0021]FIG. 3 is flowchart diagram illustrating an exemplary method forobtaining updated atrial arrhythmia event status information from animplanted cardiac device in accordance with the present invention usinga patient activator communication device in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] An exemplary implantable cardiac device 10 which may becontrolled by a patient activator communication device 12 to provideatrial arrhythmia event status and other information to a patient and toprovide patient controlled atrial shock therapy in accordance with thepresent invention is illustrated in, and will be described in detailwith reference to, FIG. 1. Although described in detail herein withreference to an implantable device 10 having the primary function ofdetecting and treating atrial arrhythmias, it should be understood thatthe present invention may be employed with an implantable device whichalso performs other functions, such as ventricular monitoring andtherapy and single or dual chamber bradycardia pacing.

[0023] The implantable cardiac device 10 includes a hermetically sealedcanister 14 which encloses circuitry for detecting and analyzing cardiacarrhythmias and for providing electrical shock therapy to treat sucharrhythmias. The circuitry within the canister 14 is connected via oneor more leads 16 to one or more electrodes 18 which are implanted in ornear the chambers of a patient's heart 20. The electrodes 18 pick upelectrical signals produced in the chambers of the heart 20 and provideelectrical contact for electrical pulses or shocks which are deliveredto the chambers of the heart 20 to pace or defibrillate/cardiovert theheart 20. Depending upon the specific applications and functionality ofthe implantable cardiac device 10, electrodes 18 may be positioned in ornear the atria, ventricles, or, preferably, both the atria andventricles of the heart 20. In an implantable cardiac device 10 inaccordance with the present invention for detecting atrial arrhythmias,and providing atrial shock therapy to terminate such atrial arrhythmias,for example, electrodes 18 are positioned in or near the atria, fordetecting atrial activity and providing atrial shock therapy to theatria, as well as in the ventricles, for detecting ventricular activity,e.g., for use in verifying the presence of atrial arrhythmias and insynchronizing the providing of atrial cardioversion shock pulses to theatria with ventricular events. A plurality of leads 16 may be requiredto connect the electrodes 18 positioned in the heart 20 to the circuitrywithin the device canister 14. As is known in the art, multipleelectrodes 18 may be coupled to the circuitry within the canister 14 viaa single one of the leads 16. The canister 14, leads 16, and electrodes18 are preferably designed such that the entire device 10 is implantablebeneath the skin of a patient.

[0024] The leads 16 connect the electrodes 18 positioned within theheart 20 to signal detection circuitry 22 within the implantable devicecanister 14. The signal detection circuitry 22 may be implemented in aconventional manner to provide atrial and/or ventricular activitysignals based on the cardiac signals picked up at the electrodes 18.Conventional signal detection circuitry 22 may include signal amplifiersand filters, and may include, in addition, circuitry for detectingatrial and ventricular depolarizations and for providing atrial andventricular depolarization detection indication signals in responsethereto, along with circuitry for obtaining electrogram signals and forproviding digitized electrograms from the cardiac signals detected atthe electrodes 18.

[0025] The signals provided by the signal detection circuitry 22 areprovided to an implantable device system processor 24. The systemprocessor 24 may be implemented, for example, as one or moreconventional microprocessors with associated memory 26. Memory 26 may bean integral part of, or separated from, but coupled to, the processor24. Memory 26 is employed in a conventional manner to store data, suchas cardiac activity data, for analysis by the processor 24, as well asto store the programming instructions which control the functionsperformed by the processor 24. For example, programming instructions forimplementing an atrial arrhythmia detection algorithm 28 by theprocessor 24, and for operating the processor 24 to generate messages 30indicative of the status of an atrial arrhythmia event detected by theimplanted device 10, the availability of atrial shock therapy, etc., maybe stored in memory 26. These functions will be described in more detailbelow. Of course, other general and conventional programminginstructions for the processor 24 may also be stored in memory 26.

[0026] The implantable cardiac device 10 also includes conventionalcardioverter/defibrillator circuitry 32 for applying electrical energyto the heart 20 via the leads 16 and electrodes 18 positioned in theheart. In response to the detection of an atrial arrhythmia by theprocessor 24, based on cardiac signals provided by the signal detector22, the processor 24 controls the cardioverter/defibrillator to provideelectrical shock therapy to the heart 20 to terminate the atrialarrhythmia event. The type of electrical shock therapy provided to theheart 20 may depend upon the type of atrial arrhythmia event identified.For example, the cardioverter/defibrillator circuitry 32 may becontrolled by the processor 24 to provide a relatively high voltagelevel atrial defibrillation pulse to the atria of the heart 20 toterminate an atrial fibrillation or flutter event. Such relatively highvoltage shock therapy is preferably provided in synchronism with adetected or paced ventricular event, in order to prevent the atrialshock therapy from initiating a more serious ventricular arrhythmia. Inresponse to the detection of a high-rate, but more regular, atrialarrhythmia, e.g., atrial tachycardia, the processor 24 may control thecardioverter/defibrillator circuitry 32 to provide atrialantitachycardia pacing to the atria to terminate the atrial arrhythmiaevent. Atrial antitachycardia pacing may typically include a rapidseries of atrial pacing pulses delivered to the atria via a pacing lead16 and one or more electrodes 18 positioned in or near the atria of theheart 20. Various atrial shock therapies are known to those skilled inthe art, and will not be described in further detail herein.

[0027] The implantable device 10 may include receiver/transmittercircuitry 34 including an antenna coil 36. The receiver/transmitter 34may be implemented in a conventional manner to transmit data from thesystem processor 24 out of the implanted device 10 to a remoteprogrammer device 38. For example, cardiac activity data detected by thesignal detector circuitry 22 may be transmitted to the externalprogrammer device 38 to be stored and analyzed therein in more detailthan is possible in the implanted device 10 itself. Thereceiver/transmitter 34 may also receive programming instructions fromthe external programmer device 38 for, for example, programmingoperating parameters of the implantable cardiac device 10. Communicationbetween the receiver/transmitter 34 and the external programmer device38 may be implemented in a conventional manner, e.g., via a telemetry(e.g., RF) link. It is noted that the external programmer device 38 is arelatively large and sophisticated device which is typically employed bya physician to monitor and control operation of the implantable device10.

[0028] In accordance with the present invention, the implantable cardiacdevice 10 may also include a reed switch 40 mounted therein and coupledto the system processor 24. As will be discussed in more detail below,the reed switch 40 is operated (closed or opened) by the application ofa magnetic field near the site of implantation in a patient of theimplantable cardiac device 10. The system processor 24 detects theoperation of the reed switch 40 as a patient activation request. Inresponse to the patient activation request, the system processor 24initiates a patient activation operation to provide an indication to thepatient of atrial arrhythmia event status and atrial shock therapyavailability, and to allow the patient to control the delivery of atrialshock therapy, as will be described in more detail below.

[0029] In accordance with the present invention, the implantable cardiacdevice 10 may preferably also include tone generation circuitry 42. Thetone generation circuitry 42 may be implemented in a conventionalmanner, and is controlled by the system processor 24 to drive a smallspeaker 44 to produce different tones of sufficient volume to be audibleby a patient in which the implantable device 10 is implanted. As will bediscussed in more detail below, the tones produced by the tonegeneration circuitry 42 and speaker 44 may be used to indicate to apatient the status of an ongoing atrial arrhythmia event and theavailability of atrial shock therapy.

[0030] The implantable cardiac device 10 also includes a battery 46,which provides power for the processor 24 and other circuit componentsof the implantable cardiac device 10.

[0031] The circuitry for implementing the signal detector 22, processor24, cardioverter/defibrillator 32, receiver/transmitter 34, toneproducer 42, and other functions of the implantable cardiac device 10may be implemented in a conventional manner using analog or digitalcircuitry, including one or more microprocessors, or any combinationthereof. As will be known to those skilled in the art, functionsperformed by the signal detector 22, cardioverter/defibrillator 32,receiver/transmitter 34, and tone producer 42, may be performed byindependent analog and/or digital circuitry, as suggested by theillustration of FIG. 1, or may be implemented in one or more processors24, or with a combination of independent circuits and one or moreprocessors.

[0032] In accordance with the present invention, a patient in which theimplantable cardiac device 10 is implanted may employ a patientactivator communication device 12 to request an indication from theimplanted cardiac device 10 of the status of atrial arrhythmia eventsdetected by the implanted device 10 and the availability of atrial shocktherapy, as well as to control the providing of atrial shock therapy bythe implanted device 10. The patient activator 12 is preferably designedto be portable, and is preferably small in size and able to be heldeasily in the hand and manipulated by a patient. Various componentswhich may be implemented in an activator 12 in accordance with thepresent invention are illustrated schematically in FIG. 2.

[0033] The activator 12 may preferably include a magnet 48 mountedtherein. (In its simplest form, a patient activator 12 in accordancewith the present invention may be implemented with a magnet 48 alone).When the patient activator 12 is positioned near the implant site of theimplantable device 10 the magnetic field generated by the magnet 48 inthe activator 12 operates the reed switch 40 coupled to the processor 24in the implantable device 10. Operation of the reed switch 40 in thismanner for at least a minimal period of time, e.g., one second, isrecognized by the implanted device processor 24 as a patient activationrequest which initiates a patient-activation operation by the processor24. During the patient-activation operation, the processor 24 employs amessage generator function 30 to generate a status message which isprovided to the patient to indicate the status of atrial arrhythmiaevents which are identified by the processor. Atrial arrhythmia eventstatus messages may be provided to the patient, as described above, bycontrolling tone generation circuitry 42 in the implantable device 10 togenerate a tone audible to the patient to indicate the status of anatrial arrhythmia event.

[0034] The atrial arrhythmia event status message generated by theimplantable device 10 may also preferably be provided in a visual formto the patient, e.g., in a visual display provided on the patientactivator 12. For example, the activator 12 may include tone detectioncircuitry 50. The tone detection circuitry 50 may be implemented in aconventional manner to detect the tones produced by the tone generationcircuitry 42 in the implantable cardiac device 10 and to generateelectrical signals in response thereto. The electrical signals generatedby the tone detection circuitry 50 in the activator 12 are provided toan activator processor 52, which decodes the signals provided by thetone detection circuitry. The activator 12 also includes conventionaldisplay circuitry 54. The display circuitry 54 is driven by theactivator processor 52, in response to the signals received from thetone detection circuitry 50, to provide a visual indication to thepatient of the atrial arrhythmia event status indication provided by theimplantable cardiac device 10. For example, the display circuitry 54 mayinclude one or more LEDs or lamps 56 which are illuminated in aconventional manner to indicate, e.g., the receipt of a patientactivation request by the implanted device 10, the presence or absenceof an atrial arrhythmia event, the availability of atrial shock therapy,etc., as will be described in more detail below.

[0035] As an alternative to the magnet 48, for providing an activationrequest to the implanted cardiac device 10, and tone detector circuitry50, for detecting atrial arrhythmia event status indication messagesprovided by the implanted device 10, the activator 12 may includeconventional receiver/transmitter circuitry 58, including an antenna 59.The activator receiver/transmitter 58 may be implemented in aconventional manner, and may be coupled to the receiver/transmitter 34(or another similar circuit) in the implanted device 10, via a telemetry(e.g., RF) link, to both provide patient activation request signals toand receive status information from the implanted cardiac device 10. Theactivator receiver/transmitter 58 is coupled to, and controlled by, theactivator processor 52. Patient input circuitry 60 is preferably alsoprovided in the activator 12 and coupled to the activator processor 52.The activator input circuitry 60 may include conventional buttons,switches, dials, etc., and related electronic circuitry. A patientemploys the activator input circuitry 60 to initiate a patientactivation operation in the implanted device 10. For example, thepatient may push a button on the activator 12, which is part of theinput circuitry 60, to request the status of an ongoing atrialarrhythmia. A signal generated by the activator input circuitry 60 isreceived by the processor 52 which, in turn, generates a command signalrequesting, e.g., an updated atrial arrhythmia status indication fromthe implanted device 10. This command message is, in turn, provided tothe activator receiver/transmitter 58, to be transmitted to theimplanted device 10, e.g., via the receiver/transmitter 34 therein, overthe telemetry link. The received command signal is, in turn, processedby the implanted device processor 24. In response to the request, amessage indicating, e.g., atrial arrhythmia event status, is generatedby the implanted device processor 24, and provided to the implanteddevice receiver/transmitter 34 for transmission back to the activator12. The status message is received by the activator receiver/transmitter58 and provided to the activator processor 52. The activator processor52 processes the atrial arrhythmia status indication message receivedfrom the implanted device 10, and generates therefrom an indication ofongoing atrial arrhythmia status, which, e.g., may be presented to thepatient by controlling the activator display 54. Of course, theindication may be provided visually, audibly, and/or in any other mannerto a patient on the activator 12. Other status information, such asshock therapy availability, may also be requested from the implanteddevice 10 using the input 60 and receiver/transmitter circuitry 58. Suchtelemetry circuitry may also be employed to request or withhold theproviding of shock therapy by the implanted device 10. It should benoted that a patient activator 12 will typically include either thereceiver/transmitter 58 and input circuitry 60 or a magnet 48 and tonedetector 50, but may include both systems, as illustrated in FIG. 2.

[0036] An exemplary process in accordance with the present invention forproviding patient control and monitoring of atrial shock therapyprovided by an implanted cardiac device 10 will now be described indetail with reference to the exemplary flowchart diagram of FIG. 3. Inaccordance with the present invention, the implanted device 10 maydetermine automatically at 64 the presence or absence of an atrialarrhythmia, e.g., atrial tachycardia, fibrillation, or flutter, withouta specific request to do so from external to the patient. For example,conventional methods may be used by the implanted device processor 24 tomonitor ventricular and/or atrial activity detected by the signaldetector 22 to determine the likelihood of the occurrence of an atrialarrhythmia. If conditions indicate that an atrial arrhythmia is likely,the processor 24 may employ one or more conventional atrial arrhythmiadetection algorithms 28 to determine if an atrial arrhythmia isoccurring, and the nature of the arrhythmia.

[0037] The implanted device processor 24 also continually checks for thereceipt of an activation request from the patient activator 12 at 66. Asdescribed above, such a request may be provided by a magnet 48 in theactivator 12 positioned near the implanted device 10, to operate thereed switch 40, which, in turn, is detected by the processor 24.Alternatively, an activation request signal may be sent to the implanteddevice processor 24 via a telemetry link established between theactivator receiver/transmitter 58 and the implanted devicereceiver/transmitter 34. If an activation request 66 is not detected bythe implanted device processor 24, the processor 24 continues to monitorthe status of a detected atrial arrhythmia 64, continually updatingongoing atrial arrhythmia status, while continually checking for receiptof an activation request 66, until such a request is received.

[0038] If an activation request 66 is received by the implanted deviceprocessor 24, the processor 24 generates a confirmation message orsignal at 68, e.g., employing the message generator function 30 storedin memory 26, to provide confirmation to a patient that the activationrequest has been received by the implanted device 10. The confirmationsignal or message may be in the form of a message transmitted from theimplanted device receiver/transmitter 34 to the activatorreceiver/transmitter 58 and displayed or otherwise presented on theactivator 12 by the activator processor 52, e.g., on the activatordisplay 54. Alternatively, the confirmation signal may be provided as atone produced by the tone producer 42 and speaker 44 in the implanteddevice 10 and audible by the patient, and/or received by the tonedetector 50 in the activator 12 and translated to a visual signaldisplayed on the activator display 54.

[0039] The implanted device processor 24 then determines the currentupdated status 70 of any atrial arrhythmia which may be occurring in thepatient's heart 20 and which has been detected by the implanted device10. If an atrial arrhythmia is occurring, the current status of theatrial arrhythmia is indicated to the patient at 72. If no arrhythmia isoccurring, this fact may also be indicated at 74, or simply no positiveindication of atrial arrhythmia is provided. The indication of thecurrent status of an atrial arrhythmia may be generated by the implanteddevice processor 24 employing the message generator function 30. Themessage indicating the status of an ongoing atrial arrhythmia may beprovided via the implanted device receiver/transmitter 34 and activatorreceiver/transmitter 58 to the activator 12 for display or otherpresentation thereon. Alternatively, the status of an ongoing atrialarrhythmia may be provided as an audible tone generated by the implanteddevice tone producer circuitry 42 and speaker 44, and audible to thepatient and/or received by the activator tone detector 50 and translatedinto a visual display on the activator 12.

[0040] After providing an indication to a patient of the current ongoingstatus of an atrial arrhythmia, the processor 24 may return tomonitoring and updating the status of the atrial arrhythmia 64 andwaiting for a subsequent activation request 66 from the activator 12. Aslong as an activation request 66 is active, e.g., as long as the patientactivator 12 is in position to operate the reed switch 40, the implanteddevice processor 24 may provide automatically periodically updatedatrial arrhythmia status indications to the patient in the mannerdescribed. Such updated status indications may be providedautomatically, as long as the activation request 66 is active, at eachoccurrence of a selected cardiac event, e.g., a ventricular event.

[0041] The implanted device processor 24 may also determine whetheratrial shock therapy is available at 76, and provide an indication ofatrial shock therapy availability to the patient at 78 and 80, e.g., inthe form of a message transmitted from the implanted device 10 to theactivator 12 via a telemetry link, and/or as an audible tone. Forexample, shock therapy may be indicated as available if severalpredetermined conditions are satisfied. Such conditions may include, forexample, the presence of an ongoing atrial arrhythmia, the programmingON of shock therapy by a physician (using the programmer 38), the factthat shock therapy had not just been attempted for the ongoing atrialarrhythmia event, and the satisfaction of one or more verificationconditions, such as a detected atrial rate exceeding the detectedventricular rate, thereby confirming an atrial only arrhythmia. Otherconditions for determining whether or not shock therapy is availablemay, of course, also be employed.

[0042] It should be understood that not all of the steps illustratedschematically in FIG. 3 need be performed, and the steps illustrated maybe performed in a different order, in accordance with the presentinvention. For example, the steps of confirming an activation request68, indicating the presence or absence of an atrial arrhythmia 72, 74,and indicating the availability of shock therapy 78, 80 may be performedessentially simultaneously. These three pieces of information may beprovided to a patient using a minimal number of three distinctivelydifferent tones produced by the tone producer 42 and speaker 44. A firsttone may indicate that there is no ongoing atrial arrhythmia (and thusthat atrial shock therapy is not available). A second tone may indicatethat there is an ongoing atrial arrhythmia, but that atrial shocktherapy is not available. A third tone may indicate that there is anongoing atrial arrhythmia, and that atrial shock therapy is available.The production of any tone by the implanted device 10 confirms that anactivation request has been received thereby from the activator 12.

[0043] An important feature of the present invention, as illustrated inFIG. 3, is that the determination of the status of an atrial arrhythmiaby the implanted device processor 24 is performed automatically by theprocessor 24 independently of the receipt of an activation request froma patient. As along as an atrial arrhythmia is ongoing, the processor 24continues to monitor and update the status of the atrial arrhythmiaperiodically, e.g., at each occurrence of a selected cardiac, e.g.,ventricular, event. Thus, the current status of an ongoing atrialarrhythmia is readily available to be presented to a patient on requestusing the activator 12. Reinitiation of atrial arrhythmia detection bythe implanted device processor 24 is not required each time the patientrequests an atrial arrhythmia status indication update.

[0044] A patient informed as to the ongoing status of an atrialarrhythmia using a system and method in accordance with the presentinvention preferably is able to employ such information to control theoperation of the implanted device 10 to provide atrial shock therapy.For example, a patient may feel the onset of what he may believe to bean atrial arrhythmia. By use of the activator device 12, the patient isable to confirm whether or not an atrial arrhythmia is occurring. Theactivator 12 may then also be employed to request the implanted device10 to proceed with providing atrial shock therapy to terminate theatrial arrhythmia (if such shock therapy is indicated as beingavailable), or to withhold the providing of such therapy by theimplanted device 10. For example, a patient may wish to withholdimmediate atrial shock therapy until the patient is better prepared forthe therapy, at which point the activator device 12 may be employed toinitiate a shock therapy request.

[0045] Patient controlled requesting and withholding of atrial shocktherapy may be initiated by a patient using the activator inputcircuitry 60. The proper command signal may then be transmitted to theimplanted device 10 over the telemetry link between activatorreceiver/transmitter 58 and implanted device receiver/transmitter 34.Alternatively, the requesting and withholding of shock therapy may beperformed using a more simple activator device 12 including a magnet 48.For example, as discussed above, by positioning the activator magnet 48near the implanted device 10, to operate the reed switch 40, a patientactivation operation is initiated in the implanted device 10. If theactivation request is thus presented to the implanted device 10 for lessthan a threshold duration (e.g., less than seven seconds), the patientmay thereby instruct the implanted device processor 24 to withhold theproviding of atrial shock therapy. If the activator 12 is maintained inposition for longer than the threshold duration (e.g., greater thanseven seconds), the implanted device processor 24 may be instructed toproceed with providing atrial shock therapy, either immediately or oncethe activator 12 is removed from position near the implanted device 10.Any shock therapy initiated in the implanted device 10 may be disabledby maintaining the activator 12 in position for at least a stop therapythreshold duration, which may be much longer than the threshold durationrequired to initiate therapy. For example, any shock therapy initiatedin the implanted device 10 may be disabled if the activator 12 ismaintained in position for longer than a stop therapy threshold durationof, e.g., sixty seconds. Shock therapy may be reinitiated following sucha stop therapy operation by removing the activator 12 from position nearthe implanted device 10 and then replacing the activator 12 in positionnear the implanted device 10 for at least the initial duration requiredto re-initiate a patient activation operation. (Preferably, all atrialshock therapy is disabled during application of the activator magnet 48near the implanted device 10.)

[0046] Of course, as discussed above, by positioning the activatormagnet 48 near the implanted device 10, the patient also requests anindication of the ongoing status of an atrial arrhythmia. Thus, a simpleactivator device 12 employing a magnet 48 may be used both to request anatrial arrhythmia status indication from an implanted device 10 inaccordance with the present invention (by the presence of the thusgenerated activation signal), as well as to control the operation of theimplanted device 10 to provide atrial shock therapy (by the duration ofthe presence of the thus generated activation signal). Since relativelycomplicated activator receiver/transmitter 58, input 60, and othercircuitry are not required, a relatively inexpensive and simple tooperate activator device 12 may thus be employed in accordance with thepresent invention to both monitor the status of an ongoing atrialarrhythmia and to control the providing of atrial shock therapy to treatthe arrhythmia.

[0047] It is understood that the present invention is not limited to theparticular exemplary embodiments and applications thereof illustratedand described herein, but embraces such modified forms thereof as comewithin the scope of the following claims.

What is claimed is:
 1. A patient controllable atrial shock therapysystem including an implantable atrial shock therapy device, comprising:(a) an atrial arrhythmia detector for detecting an atrial arrhythmiaevent episode and updating automatically an atrial arrhythmia eventstatus periodically throughout the duration of a detected atrialarrhythmia event episode; (b) patient activation request detection meansfor detecting a patient activation request originating from external tothe implantable device; and (c) message generator means for generating amessage indicating the periodically updated arrhythmia event status inresponse to detection of the patient activation request.
 2. The patientcontrollable atrial shock therapy system of claim 1 wherein the atrialarrhythmia detector includes means for detecting atrial arrhythmia eventepisodes selected from the group of atrial arrhythmias consisting ofatrial tachycardia and atria fibrillation.
 3. The patient controllableatrial shock therapy system of claim 1 wherein the atrial arrhythmiadetector includes means for updating atrial arrhythmia event statusperiodically at each occurrence of a selected cardiac event occurringthroughout the duration of a detected atrial arrhythmia event episode.4. The patient controllable atrial shock therapy system of claim 3wherein the atrial arrhythmia detector includes means for updatingatrial arrhythmia event status periodically at each occurrence of aventricular event occurring throughout the duration of a detected atrialarrhythmia event episode.
 5. The patient controllable atrial shocktherapy system of claim 1 wherein the patient activation requestdetection means includes a reed switch responsive to a magnetic field tooperate the reed switch to provide the patient activation request. 6.The patient controllable atrial shock therapy system of claim 5 whereinthe message generator means generates messages indicating theperiodically updated arrhythmia event status as long as the magneticfield operates the reed switch.
 7. The patient controllable atrial shocktherapy system of claim 1 wherein the message generator includes meansfor generating messages indicating the periodically updated arrhythmiaevent status as long as the patient activation request is detected. 8.The patient controllable atrial shock therapy system of claim 1 whereinthe message generator means includes means for generating an audibletone indicating the periodically updated arrhythmia event status.
 9. Thepatient controllable atrial shock therapy system of claim 1 wherein thepatient activation request detection means includes a reed switchresponsive to a magnetic field to operate the reed switch to provide thepatient activation request, wherein the message generator meansgenerates the message indicating the periodically updated arrhythmiaevent status in response to operation of the reed switch, and whereinthe message generator means includes means for generating an audibletone indicating the periodically updated arrhythmia event status, andfurther comprising a hand-held activator including: (a) a magnet forgenerating the magnetic field to operate the reed switch when theactivator is positioned near the implantable device; (b) tone detectormeans for receiving the audible tone indicating the periodically updatedarrhythmia event status and converting the audible tone indicating theperiodically updated arrhythmia event status into an electrical signalindicating the periodically updated arrhythmia event status; and (c)display means responsive to the electrical signal indicating theperiodically updated arrhythmia event status for displaying on theactivator a visual indication of the periodically updated arrhythmiaevent status.
 10. The patient controllable atrial shock therapy systemof claim 1 wherein the patient activation request detection meansincludes a patient activation request receiver adapted to receive apatient activation request signal, wherein the implantable cardiacdevice comprises additionally a status message transmitter responsive tothe message generator means for transmitting a status message indicatingthe periodically updated arrhythmia event status, and further comprisinga hand-held activator including: (a) a patient activation requesttransmitter for transmitting a patient activation request signal to bereceived by the patient activation request receiver; (b) a statusmessage receiver adapted to receive the status message indicating theperiodically updated arrhythmia event status from the status messagetransmitter; and (c) display means responsive to the status messagereceived by the status message receiver for displaying on the activatora visual indication of the periodically updated arrhythmia event status.11. A patient controllable atrial shock therapy system including animplantable atrial shock therapy device, comprising: (a) an atrialarrhythmia detector for detecting an atrial arrhythmia event episode andfor providing an atrial arrhythmia event status; (b) an atrialcardioverter for providing atrial shock therapy; (c) patient activationrequest detection means for detecting a patient activation requestoriginating from external to the implantable device; (d) messagegenerator means for generating a message indicating the atrialarrhythmia event status responsive to the detection of the patientactivation request; and (e) shock therapy control means for requestingand withholding the providing of atrial shock therapy in response to aduration of the detected patient activation request.
 12. The patientcontrollable atrial shock therapy system of claim 11 wherein the atrialarrhythmia detector includes additionally means for automaticallyupdating atrial arrhythmia event status periodically throughout theduration of a detected atrial arrhythmia event episode.
 13. The patientcontrollable atrial shock therapy system of claim 12 wherein the atrialarrhythmia detector includes means for updating atrial arrhythmia eventstatus periodically at each occurrence of a selected cardiac eventoccurring throughout the duration of a detected atrial arrhythmia eventepisode.
 14. The patient controllable atrial shock therapy system ofclaim 13 wherein the atrial arrhythmia detector includes means forupdating atrial arrhythmia event status periodically at each occurrenceof a ventricular event occurring throughout the duration of a detectedatrial arrhythmia event episode.
 15. The patient controllable atrialshock therapy system of claim 11 wherein the atrial arrhythmia detectorincludes means for detecting atrial arrhythmia event episodes selectedfrom the group of atrial arrhythmias consisting of atrial tachycardiaand atrial fibrillation and wherein the atrial cardioverter includesmeans for providing atrial shock therapy selected from the group ofatrial shock therapies consisting of atrial antitachycardia pacing andatrial defibrillation shock therapy.
 16. The patient controllable atrialshock therapy system of claim 11 wherein the patient activation requestdetection means includes a reed switch responsive to a magnetic field tooperate the reed switch to provide the patient activation request, andwherein the shock therapy control means requests shock therapy inresponse to operation of the reed switch by the magnetic field forgreater than a selected duration and withholds shock therapy in responseto operation of the reed switch by the magnetic field for less than theselected duration.
 17. The patient controllable atrial shock therapysystem of claim 11 wherein the message generator means includes meansfor generating an audible tone indicating the arrhythmia event status.18. The patient controllable atrial shock therapy system of claim 11wherein the patient activation request detection means includes a reedswitch responsive to a magnetic field to operate the reed switch toprovide the patient activation request, wherein the shock therapycontrol means requests and withholds shock therapy in response to aduration of operation of the reed switch by the magnetic field, andwherein the message generator means includes means for generating anaudible tone indicating the arrhythmia event status, and furthercomprising a hand-held activator including: (a) a magnet for generatingthe magnetic field to operate the reed switch when the activator ispositioned near the implantable device; (b) tone detector means forreceiving the audible tone indicating the arrhythmia event status andconverting the audible tone indicating the arrhythmia event status intoan electrical signal indicating the arrhythmia event status; and (c)display means responsive to the electrical signal indicating thearrhythmia event status for displaying on the activator a visualindication of the arrhythmia event status.
 19. The patient controllableatrial shock therapy system of claim 11 wherein the message generatorincludes additionally means for generating a message indicating anavailability of atrial shock therapy responsive to the patientactivation request.
 20. The patient controllable atrial shock therapysystem of claim 19 wherein the message generator means includes meansfor generating an audible tone indicating the arrhythmia event statusand the availability of atrial shock therapy.
 21. The patientcontrollable atrial shock therapy system of claim 20 wherein the messagegenerator means includes means for generating a first audible toneindicating that an atrial arrhythmia event is in progress and thatatrial shock therapy is available and a second audible tonedistinguishable from the first audible tone indicating that an atrialarrhythmia event is in progress but that atrial shock therapy is notavailable.
 22. A method for controlling an implantable atrial shocktherapy device, comprising the steps of: (a) detecting an atrialarrhythmia event episode and automatically updating an atrial arrhythmiaevent status periodically throughout the duration of a detected atrialarrhythmia event episode with the implantable device; (b) providing apatient activation request to the implantable device from external tothe implantable device; and (c) generating a message from theimplantable device indicating the periodically updated arrhythmia eventstatus in response to 11receipt of the patient activation request by theimplantable device.
 23. The method of claim 22 wherein the step ofdetecting an atrial arrhythmia event episode includes the step ofdetecting atrial arrhythmia event episodes selected from the group ofatrial arrhythmias consisting of atrial tachycardia and atrialfibrillation.
 24. The method of claim 22 wherein the step ofautomatically updating an atrial arrhythmia event status includes thestep of updating atrial arrhythmia event status periodically at eachoccurrence of a selected cardiac event occurring throughout the durationof a detected atrial arrhythmia event episode.
 25. The method of claim24 wherein the step of automatically updating an atrial arrhythmia eventstatus includes the step of updating atrial arrhythmia event statusperiodically at each occurrence of a ventricular event occurringthroughout the duration of a detected atrial arrhythmia event episode.26. The method of claim 22 wherein the step of providing a patientactivation request to the implantable device from external to theimplantable device includes the step of positioning a magnet near theimplantable device.
 27. The method of claim 26 wherein the step ofgenerating a message from the implantable device indicating theperiodically updated arrhythmia event status is repeated periodically aslong as the magnet is positioned near the implantable device.
 28. Themethod of claim 22 wherein the step of generating a message from theimplantable device indicating the periodically updated arrhythmia eventstatus includes the step of generating messages indicating theperiodically updated arrhythmia event status as long as the patientactivation request is received by the implantable device.
 29. The methodof claim 22 wherein the step of generating a message from theimplantable device indicating the periodically updated arrhythmia eventstatus includes the step of generating an audible tone indicating theperiodically updated arrhythmia event status.
 30. The method of claim 29comprising additionally the step of generating a visual indication ofthe periodically updated arrhythmia event status from the audible toneindicating the periodically updated arrhythmia event status.
 31. Themethod of claim 22 wherein the step of providing a patient activationrequest to the implantable device from external to the device includesthe step of transmitting a patient activation request signal to theimplantable device and wherein the step of generating a message from theimplantable device indicating the periodically updated arrhythmia eventstatus includes the step of transmitting a message from the implantabledevice indicating the periodically updated arrhythmia event status. 32.The method of claim 31comprising additionally the step of displaying avisual indication of the periodically updated arrhythmia event statusresponsive to the message transmitted from the implantable deviceindicating the periodically updated arrhythmia event status.
 33. Amethod of controlling an implantable atrial shock therapy device,comprising the steps of: (a) detecting an atrial arrhythmia eventepisode and providing an atrial arrhythmia event status with theimplantable device; (b) detecting a patient activation requestoriginating from external to the implantable device; (c) generating amessage from the implantable device indicating the arrhythmia eventstatus responsive to the detection of the patient activation request;and (d) requesting and withholding providing of atrial shock therapy bythe implantable device in response to a duration of detection of thedetected patient activation request.
 34. The method of claim 33comprising additionally the step of automatically updating atrialarrhythmia event status periodically throughout the duration of adetected atrial arrhythmia event episode with the implantable device.35. The method of claim 34 wherein the step of automatically updatingatrial arrhythmia event status includes the step of updating atrialarrhythmia event status periodically at each occurrence of a selectedcardiac event occurring throughout the duration of a detected atrialarrhythmia event episode.
 36. The method of claim 35 wherein the step ofautomatically updating atrial arrhythmia event status includes the stepof updating atrial arrhythmia event status periodically at eachoccurrence of a ventricular event occurring throughout the duration of adetected atrial arrhythmia event episode.
 37. The method of claim 33wherein the step of detecting an atrial arrhythmia event episodeincludes the step of detecting atrial arrhythmia event episodes selectedfrom the group of atrial arrhythmias consisting of atrial tachycardiaand atrial fibrillation.
 38. The method of claim 33 wherein the step ofdetecting a patient activation request originating from external to thepatient includes the step of detecting a magnetic field positioned nearthe implantable device and wherein the step of requesting andwithholding atrial shock therapy includes the step of requesting shocktherapy in response to detection of the magnetic field for greater thana selected duration and withholding shock therapy in response todetection of the magnetic field for less than a selected duration. 39.The method of claim 33 wherein the step of generating a message from theimplantable device indicating the arrhythmia event status includes thestep of generating an audible tone indicating the arrhythmia eventstatus.
 40. The method of claim 39 comprising additionally the step ofgenerating a visual indication of the arrhythmia event status from theaudible tone indicating the arrhythmia event status.
 41. The method ofclaim 33 comprising additionally the step of generating a messageindicating an availability of atrial shock therapy responsive to thedetection of the patient activation request.
 42. The method of claim41wherein the step of generating a message indicating an availability ofatrial shock therapy includes the step of generating an audible toneindicating the arrhythmia event status and the availability of atrialshock therapy.
 43. The method of claim 42 wherein the step of generatingan audible tone indicating the arrhythmia event status and theavailability of atrial shock therapy includes the step of generating afirst audible tone indicating that an atrial arrhythmia event is inprogress and that atrial shock therapy is available and a second audibletone distinguishable from the first audible tone indicating that anatrial arrhythmia event is in progress but that atrial shock therapy isnot available.
 44. A patient controllable cardiac shock therapy systemincluding an implantable cardiac shock therapy device, comprising: (a)an arrhythmia detector for detecting a cardiac arrhythmia and providinga cardiac arrhythmia event status; (b) patient activation requestdetection means for detecting a patient activation request originatingfrom external to the implantable device; and (c) message generator meansfor generating audible tone messages within the implantable deviceindicating the cardiac arrhythmia event status in response to detectionof the patient activation request.
 45. A method for controlling animplantable cardiac shock therapy device, comprising the steps of: (a)detecting a cardiac arrhythmia and providing a cardiac arrhythmia eventstatus with the implantable device; (b) providing a patient activationrequest to the implantable device from external to the implantabledevice; and (c) generating audible tone messages from the implantabledevice indicating the cardiac arrhythmia event status in response toreceipt of the patient activation request by the implantable device. 46.The method of claim 45 comprising additionally the step of generating avisual indication of the arrhythmia event status from the audible tonemessages indicating the arrhythmia event status.
 47. A handheldactivator device for controlling an implantable shock therapy device,comprising: (a) a magnet positioned in the activator device forproviding activation signals to the implantable shock therapy device;(b) tone detector means within the activator device for receivingaudible tone status messages from the implantable shock therapy deviceand converting the audible tone status messages into electrical signalstatus messages; and (c) display means responsive to the electricalsignal status messages for displaying on the activation device a visualrepresentation of the status messages.